water vapor
B1technical/scientific, everyday
Definition
Meaning
Water in its gaseous state, typically invisible and formed by evaporation or boiling.
In atmospheric science, water vapour is a key greenhouse gas and driver of weather systems. In domestic contexts, it refers to the steam visible when water condenses in air.
Linguistics
Semantic Notes
In everyday use, often conflated with 'steam' (visible condensed water droplets). In science, strictly the gaseous phase. 'Vapour' (UK) / 'vapor' (US) spelling difference applies.
Dialectal Variation
British vs American Usage
Differences
Spelling: 'vapour' (UK) vs. 'vapor' (US). Pronunciation of 'vapour' /ˈveɪpə/ (UK) vs. 'vapor' /ˈveɪpɚ/ (US).
Connotations
Identical scientific meaning. In general discourse, both spellings are understood.
Frequency
Slightly higher frequency in UK English due to spelling conformity with other '-our' words (e.g., colour, flavour).
Vocabulary
Collocations
Grammar
Valency Patterns
[Subject] contains water vapour[Subject] releases water vapour into [Location]The amount of water vapour [is/climbs/falls]Vocabulary
Synonyms
Strong
Neutral
Weak
Vocabulary
Antonyms
Phrases
Idioms & Phrases
- “It's not the heat, it's the humidity (related concept)”
- “Steam coming out of one's ears (figurative, uses visible vapour)”
Usage
Context Usage
Business
Rare, except in industries like HVAC, construction (e.g., 'managing water vapour transmission in building materials').
Academic
Common in chemistry, physics, geography, and environmental science texts.
Everyday
Common when discussing weather, cooking, bathrooms (e.g., 'The mirror fogs up from water vapour').
Technical
Precise term in meteorology, climatology, and engineering.
Examples
By Part of Speech
verb
British English
- Water will vapourise at 100°C.
- The warm soil caused the puddle to vapourise slowly.
American English
- Water will vaporize at 212°F.
- The sun quickly vaporized the morning dew.
adverb
British English
- Not commonly used adverbially.
American English
- Not commonly used adverbially.
adjective
British English
- The vapour pressure was recorded.
- They installed a vapour barrier in the loft.
American English
- The vapor pressure reading is critical.
- A vapor barrier is required by code.
Examples
By CEFR Level
- Hot tea makes water vapour.
- There is water vapour in clouds.
- When water boils, it turns into water vapour.
- The air feels sticky because it contains a lot of water vapour.
- Scientists measure the concentration of water vapour to predict storm development.
- The cold surface caused the water vapour in the air to condense into droplets.
- Fluctuations in stratospheric water vapour concentrations can influence the rate of global warming.
- The engineering specification called for a membrane with a precisely defined water vapour transmission rate.
Learning
Memory Aids
Mnemonic
VAPOUR contains 'OUR' – think of the UK spelling 'vapour' as something shared by 'our' atmosphere.
Conceptual Metaphor
WATER VAPOUR IS A BLANKET (traps heat). WATER VAPOUR IS A FUEL (for storms).
Watch out
Common Pitfalls
Translation Traps (for Russian speakers)
- Avoid direct calque 'водяной пар' for all contexts; in science it's correct, but for 'steam' from a kettle, 'steam' is more common.
Common Mistakes
- Using 'steam' and 'water vapour' interchangeably in scientific contexts (steam can refer to visible wet vapour).
- Misspelling based on variety: writing 'vapor' in a UK text or 'vapour' in a US text.
- Incorrect article: 'a water vapour' (uncountable).
Practice
Quiz
Which process directly produces water vapour?
FAQ
Frequently Asked Questions
Pure water vapour is invisible. The 'steam' you see above a boiling kettle is actually tiny liquid water droplets that have condensed from the vapour.
Water vapour is the gas itself. Humidity is a measure of how much water vapour is in the air (often expressed as a percentage relative to the maximum possible at that temperature).
It is the most significant greenhouse gas. It absorbs heat radiated from the Earth's surface and re-radiates it, warming the atmosphere. Its concentration also affects cloud formation and precipitation.
Yes. Evaporation occurs at all temperatures. Water vapour is always present in the air unless it is completely dry; its maximum possible amount just increases with temperature.